1. Field of the Invention
This invention relates to an improvement taking the form of lens means in radiation energy integrating spheres as used, for example, though by no means exclusively, in spectroscopic quantitative sample analysis systems.
2. Description of the Prior Art
The use of radiation energy integrating spheres in, for example, spectroscopic quantitative sample analysis systems, is known in the prior art to give rise to the problem of collection by the integrating sphere of the instrumental, i.e., instrument generated, specularly--and non sample information-bearing--reflected radiation energy from the viewing windows of the sphere and sample cell, with attendant reduction in sample analysis accuracy. The prior art solutions to this problem generally involve either the enlargement of the radiation energy entry port of the integrating sphere to an extent sufficient to enable substantially all of the instrumental, specularly reflected radiation energy to exit the sphere therethrough without impingement on the interior wall surfaces of the sphere, and/or the masking of the interior wall surfaces of the sphere adjacent a radiation energy entry port of the minimum optically required size to an extent sufficient to absorb substantially all of the instrumental, specularly reflected radiation energy. In each instance, these solutions, although generally satisfactory with regard to preventing the collection of the instrumental, specularly reflected radiation energy by the integrating sphere, significantly reduce the amount of the internal surface area of the integrating sphere which can operate to collect the sample information-bearing diffusely reflected radiation energy of interest, with attendant significant reduction in the optical gain of the integrating sphere and thus in the overall accuracy of the sample analysis process.
Austrian Pat. No. 218277 discloses the reduction or elimination of artifacts in optical sample analysis systems. In those systems, however, the sample-containing sphere is not an integrating sphere, and no lens means are utilized to the above purposes.
U.S. Pat. No. 4,310,249 discloses the use of an integrating sphere in conjunction with a cylindrical sample container that can behave like a cylindrical lens. No means are included in this disclosure to discriminate between specularly, as opposed to diffusely, reflected radiation energy to improve sample analysis accuracy.
U.S. Pat. Nos. 3,515,489, 3,554,650 and 3,827,811 respectively disclose optical systems comprising reflective elements and lenses. No means are disclosed in any of these systems to discriminate between specularly, as opposed to diffusely, reflected radiation energy for any purposes.